President Barack Obama has made these ads a centerpiece of his political argument, attacking pro-Republican groups for running the ads and suggesting foreign money may be helping to pay the bill.

The new poll found four in 10 voters have seen TV ads produced by outside groups, which are run independently of political parties and candidates. It found 55% think they make a negative contribution to the election, vs. just 11% who see a positive contribution.

But despite the low standing in which voters hold these ads, the Journal’s pollsters were skeptical that Mr. Obama’s line of attack is effective.

Voters care much more about the economy and other critical issues than about TV ads, which are essentially a “process issue,” said Democratic pollster Peter D. Hart, who conducts the poll with Republican Bill McInturff. “This ends up as a side road or a cul-de-sac and it doesn’t take the Democrats anywhere.”

Mr. McInturff added that while people may not like the ads in theory, they are effective in shaping opinion.

“I think it was a mistake and a waste of time” for Mr. Obama to talk about the issue, he said. “Any day you’re spending talking about who’s sponsoring advertising … is a wasted day.”

But Mr. Hart says the Obama attacks served a useful purpose. “It changed the conversation, moved it from where the Democrats have been totally defensive, into a position where the Republicans and the press had to talk about it,” he said. “But do I see this as a closing argument? No.”